In reply to Mrs King.

i'm not sure there's a simple answer. Every design problem is different and so every design solution must be different.

I guess my answer to the question would be a good design solution is one that solves the problem well. At a minimum a good solution will work. Beyond the minimum it might delight or it might solve the problem in an elegant way or it might point the way toward a solution to other problems.

It's a simple question, but one that's no simple to answer.